PRINTING OF POROUS SUBSTRATES

Abstract: Process for the printing of porous substrate surfaces comprising: (a) etching the surface of the substrate, to render it porous, by contacting the surface of the substrate with a strong inorganic or strong organic acid; and then, in either sequence; (b) impregnating the porous substrate surface so obtained with a metal salt or a water-soluble cationic metal complex; and (c) thermotransfer printing the porous substrate surface, using a disperse dye which is capable of forming a chelate compound with the metal cation of the metal salt.

Description: Printing of Porous Substrates The present invention relates to a process for the light-fast colouration of porous substrates, especially glass fibres, without the use of a binder. It is already known to print or dye substrates such as glass fibres with cationic dyes. For example, in US 4543 103, cationic dyes are fixed on glass fibres from aqueous solution. While acceptable light fastness properties are obtained thereby for deep shades, for reasons of inadequate fixing, the dyes tend to become partly detached from the fibre, merely on contact with warm water. In the case of light shades, the light fastness of cationic dyes on glass fibres is decidedly poor. In French Patent No. 2 217 158, a method is described in which, rather than using the glass fibre surface itself as a dye receiver, there is used instead a polyvinyl chloride layer, which has previously been applied to the glass fibre surface. On exposure to high temperatures, however, the polyvinyl chloride layer is decomposed producing undesirable toxic and combustible vapours. It is also known, in Romanian Patent 76643 B, to produce thermotransfer prints on acid-treated glass fibre fabrics. Firstly, an acid treatment is applied to produce a porous layer on the fabric surface. Dispersion dyes are then incorporated into this layer without the need to use further auxiliaries. A lightf astness level of 4 or 5 can only be attained by this method, however, with a few dyes, and then only in deep shades. For light shades, using these dyes, the lightfastness falls to below 2. A method has now been found for achieving lightfast prints on porous surfaces, without the use of binder auxiliaries and using a wide range of dyes and shade levels. Accordingly, the present invention provides a process for the printing of porous substrate surfaces, especially glass fibres, comprising a) etching the surface of the substrate, to render it porous, by contacting the surface of the substrate with a strong inorganic or strong organic acid; and then, in either sequence, b) impregnating the porous substrate surface so obtained with a metal salt or a water-soluble cationic metal complex; and c) thermotransfer printing the porous substrate surface, using a disperse dye which is capable of forming a chelate compound with the metal. Preferably, step b) is conducted before step c). The initial etching step of the process of the present invention may be carried out using a conventional inorganic mineral acid such as hydrochloric acid or nitric acid but, in particular, sulphuric acid. Alternatively, there may be used a strong organic acid, that is an organic acid having a pK value within the range of from 0 to 4, e.g. formic or acetic acid. Normally, the initial etching step would be conducted by contacting the surface of the substrate with an aqueous solution containing the acid and optionally one or more conventional etching auxiliaries, in particular surfactants, more especially nonionic surfactants. Examples of such nonionic surfactants include polyoxyethylene alkyl ethers having the formula R a O(CH 2 CH 2 O) n H in which R^ is a C 12 -C 18 aliphatic group and n ranges from 4 to 20; polyoxyethylene phenol ethers having the formula R b -C 6 H 4 -O-(CH 2 CH 2 O) m H in which R b is a C 8 -C 12 aliphatic group and m ranges from 4 to 50; sorbitan partial fatty acid esters e.g. sorbitan monolaurate, sorbitan distearate or sorbitan trioleate; polyoxyethylene acyl esters having the formula R b CO 2 (CH 2 CH 2 O) m H in which R b and m have their previous significance; oxyethylene - oxypropylene block polymers having a molecular weight ranging from 1000 to 10,000; and fatty acid monoglycerides having the formula I^OCH 2 -CH(OH)-CH 2 OH in which R,. is a C 8 -C 18 acyl group. Polyoxyethylene phenol ethers of formula R_,O(CH 2 CH 2 O) n H in which R,- is Cs-Cgalkyl, especially C 9 alkyl, and n is 8 to 12, especially 10, are preferred. The initial etching step is conveniently conducted using sulphuric acid and is continued until the weight loss of the treated substrate ranges from 0.5 to 10 % by weight, especially from 1 to 5 % by weight, based on the original weight of the substrate. The etching may be carried out within a wide range of temperature, e.g. from 20 to 150°C and over a wide time span, e.g. from 1 to 120 minutes. With respect to the impregnation step b) this operation may be carried out, preferably on a padder using either a water-soluble metal salt or a water-soluble cationic heavy metal complex. By the term "metal" as used in this specification and the claims there is meant, a metal having an atomic number above 20 and which is capable of forming a complex with the dyestuff used in the thermotransfer printing operation. Preferred examples of such metals are the transition metals and metals of Groups lb, lib, πia, Vllb and Vπib of the Periodic System. Clearly, the metal salt used should be non-toxic and should not be strongly coloured, either when applied per se to the substrate, or on oxidation subsequent to its application to the substrate. For this reason, preferred cations for use in forming metal salts are aluminium, cobalt, manganese, nickel, zinc and, in particular, copper. Mixtures of metal cations may be used. The anions used in forming the metal salt may be a mineral acid anion such as the chloride anion and, in particular, the sulphate anion, or an organic acid anion, in particular the acetate anion. If a metal complex is used in the impregnation step b), such a complex should be water-soluble and be cationic, and should also decompose, under thermotransfer conditions, i.e. at a temperature in the range of from 150 to 300°C, with the liberation of the metal cation. If step b) is conducted after step c), the temperature must be subsequently raised to a temperature ranging from 180 to 300°C. This temperature elevation may be effected directly after step b), or in conjunction with a further treatment, e.g. the application of a polymer layer. Preferred metal complexes are those formed between the metal cation and bases such as ammonia; polyamines of formula H 2 N-CH 2 CH 2 -NH(CH 2 CH 2 NH) p H in which p is 1 to 10, especially ethylenediamine, diethylenetriamine or triethylenetetramine; ethanolamine, diethanolamine or triethanolamine; biuret; guanylurea; or biguanide. The preferred water-soluble, cationic metal complexes are the corresponding copper complexes, in particular the copper ethylenediamine complex. During the impregnation step b), it is preferred that the substrate absorbs from 0.01 to 5 %, more preferably 0.05 to 1.0 % and especially from 0.05 to 0.5 % by weight of the metal cation, based on the weight of the substrate. With respect to the thermotransfer printing step c), the printing may be carried out at normal pressure, or at a reduced pressure e.g. a vacuum ranging preferably from 900 to 100 mbar, but especially at normal pressure, using a disperse dye which is capable of forming a chelate compound with the metal used in the impregnation step. Examples of such disperse dyes are those of the azo or anthraquinone classes. Preferred azo dyes include those having the formula: in which A and B are the same or different and each is the atoms required to complete an aromatic or heteroaromatic ring system. Aromatic ring systems completed by A and/or B are, e.g., phenyl or naphthyl rings each of which may be optionally substituted with substituents such as C 1 -C 4 alkyl, C 1 -C 4 alkoxy, hydroxy, halogen or amino optionally substituted with - alkyl or C r C 4 hydroxyalkyl groups. Heteroaromatic ring systems completed by A and/or B include for example, benzthiazole or imidazole ring systems. Preferred anthraquinone disperse dyes are those having the formula: in which R is hydroxy or NHRj; Rj is hydrogen, which is optionally substituted by hydroxy or R t is phenyl which is optionally substituted by C 1 -C 4 alkyl; and R 2 , R 3 , R 4 and R 5 are the same or different and each is hydrogen, hydroxy, C r C 4 alkyl, C r C 4 alkoxy, chlorine, bromine, cyano, nitro, CONH 2 , C 1 -C 4 alkoxycarbonyl, phenoxy in which the phenyl moiety is optionally substituted by C 1 -C 4 alkyl, or phenoxysulphonyl. Particularly preferred anthraquinone disperse dyes are those having the formula: in which R R 2 , R 4 and R 5 have their previous significance; and R 6 is hydrogen, hydroxy or amino; In the formula (3) or (4), R 4 and R 5 are preferably hydrogen and R 2 is preferably hydrogen or phenoxy. The dyestuff, or mixture of dyestuffs, is conventionally applied to the surface of the substrate from a transfer sheet which normally comprises a paper support on which is printed the dyestuff contained in a printing ink medium, e.g. sodium alginate. The printing operation is conventionally conducted by placing the substrate surface and the transfer sheet, face-to-face, in a heated press, at a temperature ranging form 150° to 300°C, and continuing the transfer until transfer of the dye is complete. A time of up to 1 minute is normally adequate. After completion of the printing process, the printed substrate can be finished in conventional manner e.g. by rinsing, neutralizing and after-treating, e.g. by applying a finish or a coating, especially a steam-resistant coating on to the substrate. For this purpose, a cross-linking or polymerizable polymer or prepolymer may be applied to the substrate surface, and optionally crosslinked or cured. The prints obtained by the process of the present invention are reproducible and give level prints in light, medium and dark shades, using a wide range of disperse dyes, without the need to use a binder. The prints obtained have a very good light fastness as well as good rub - and wet fastness properties. As long as no after-treatment of the printed goods with a combustible resin is conducted, the disperse dye is the only organic compound which remains after printing. Accordingly, it is ensured that the printed product meets the requirement of DIN 4102, combustion class A In the preferred instance in which glass fibres are used as the substrate, the glass fibres are, in particular, E-fibres. The fibres may be used in a wide range of made-up forms such as flocks, yarns, fabrics, webs or non-woven fabrics. If, on the glass fibre starting material to be printed, any type of size or finish is already present, then such size or finish is preferably removed, e.g. enzymatically, prior to step a) or after step a) of the process of the present invention. The following Examples further illustrate the present invention. Parts and percentages are by weight unless otherwise stated. The temperature are in degrees Centigrade. Example 1: A) Pretreatment of substrate surface A glass fibre fabric is pretreated in a HT-dyeing apparatus in a dye bath which contains 10 g/1 sulphuric acid (96 %) and 0.5 g/1 of a non-ionic surfactant (condensation product of nonylphenol and ethylene oxide in molar ratio 1:10). The liquor ratio is 1:8. The dye bath is heated from 20°C to 60°C over 10 minutes and is then held at 60°C for 30 minutes. The liquor is drawn off and the fabric is rinsed with water. The fabric is neutralised with a liquor containing 2 g/1 ammonia solution (25 %) and again rinsed with water. B) Impregnation with copper complex Glass fibre fabric, acid-treated according to step A), is impregnated on a padder with an aqueous solution of copper ethylenediamine complex (copper content 2 g Cu^/litre of water), and squeezed out to a weight increase of 60 . The fabric is then dried at 80°C. C) Thermotransfer Printing An intermediate carrier paper, containing 1 g m 2 of a commercial form of the dyestuff C.I. Disperse Yellow 60, is laid over the fabric, impregnated in step B). The dyestuff is transferred using an iron at 230°C over 60 seconds. The print so obtained exhibits a Xenon light fastness value of 6(ISO 105/B02) and the printed product meets the requirement of DIN 4102, combustion class AL Example 2: A) Pretreatment of substrate surface The procedure described in Example 1(A) is repeated. B) Impregnation with copper complex The glass fibre fabric, acid-treated according as in step A), is impregnated on a padder with a liquor containing 0.5 g/1 of Cu 2+ , as copper acetate, and the liquor is adjusted to a pH value of 11 by the addition of aqueous ammonia solution. The fabric is squeezed out until the weight increase is 60 % and it is then dried at 80°C in a stream of air. C) Thermotransfer Printing An thermotransfer paper, containing 5 g/m 2 of a commercial form of the dyestuff C.I. Disperse Red 60, is laid on the fabric. Using an iron, the dye is transferred over 60 seconds at 230°C to produce a bordeaux-coloured print having a Xenon light fastness value of 7(ISO 105/B02) and the printed product meets the requirement of DIN 4102, combustion class AL Example 3: A) Pretreatment of substrate surface The procedure described in Example 1(A) is repeated. B) Impregnation with copper salt Without any intermediate drying, the acid-pretreated glass fabric from Example 3(A) is treated, in a HT dyeing apparatus, with an aqueous liquor containing 7 % (w/w) CuSO 4 .5 H 2 O. The liquor ratio is 1:8. The liquor is heated to 50°C over a period of 10 minutes, held at this temperature for 10 minutes and the liquor is drawn off. The fabric is rinsed with cold water and dried at 80°C in a stream of air. There is then laid over the fabric a thermotransfer paper which contains 5 g/m 2 of a commercial form of the dye Disperse Blue 19. C) Thermotransfer Printing Using an ironing press, the dye is then transferred on to the fabric over 60 seconds at 230°C. The print so obtained has a Xenon lightfasmess of 5-6(ISO 105/B02) and the printed product meets the requirement of DIN 4102, combustion class AL Example 4: A) Pretreatment of substrate surface The procedure described in Example 1(A) is repeated. B) Impregnation with copper salt The procedure described in Example 1(B) is repeated. There is then laid over the fabric a thermotransfer paper which contains 5 g/m 2 of a commercial form of the dye Disperse Orange 149. C) Thermotransfer Printing Using a heated press, the dye is then transferred on to the fabric over 60 seconds at 240°C. The print so obtained has a Xenon lightfastness of 4-5(ISO 105/B02) and the printed product meets the requirement of DIN 4102, combustion class AL

Claims: Claims 1. A process for the printing of porous substrate surfaces comprising a) etching the surface of the substrate, to render it porous, by contacting the surface of the substrate with an inorganic or strong organic acid; and then, in either sequence, b) impregnating the porous substrate surface so obtained with a metal salt or a water-soluble cationic metal complex; and c) thermotransfer printing the porous substrate surface, using a disperse dye which is capable of forming a chelate compound with the metal cation of the metal salt. 2. A process according to claim 1 in which step b) is conducted prior to step c). 3. A process according to claim 1 or 2 in which the inorganic acid is sulphuric acid. 4. A process according to any of the preceding claims in which the etching step a) is carried out in the presence of a nonionic surfactant. 5. A process according to any of the preceding claims in which step a) is continued until the weight loss of the treated substrate ranges from 0.5 to 10 % by weight, based on the original weight of the substrate. 6. A process according to claim 5 in which step a) is continued until the weight loss of the treated substrate ranges from 1 to 5 % by weight, based on the original weight of the substrate. 7. A process according to any of the preceding claims in which step b) is performed on a padder. 8. A process according to any of the preceding claims in which step b) is conducted using a metal salt. 9. A process according to claim 8 in which the anion of the salt is a mineral acid aniou. 10. A process according to claim 9 in which the anion is the sulphate anion. 11. A process according to any of claims 1 to 7 in which a metal complex is used in step b). 12. A process according to claim 11 in which the metal complex is formed between the metal cation and ammonia; a polyamine of formula H 2 N-CH 2 CH 2 -NH(CH 2 CH 2 NH) p H in which p is 1 to 10 ; ethanolamine, diethanolamine or triethanolamine; biuret; guanylurea; or biguanide. 13. A process according to claim 12 in which the polyamine is ethylenediamine, diethylenetriamine or trie thy lenetetramine. 14. A process according to any of the preceding claims in which the metal is aluminium, cobalt, manganese, nickel, zinc or copper. 15. A process according to claim 14 in which the metal is copper. 16. A process according to any of claims 1 to 7 and 11 to 15 in which the metal complex is copper ethylenediamine. 17. A process according to any of the preceding claims in which, during step b), the substrate absorbs 0.01 to 5 % by weight of the metal cation, based on the weight of the substrate. 18. A process according to claim 17 in which the substrate absorbs 0.05 to 0.5 % by weight of the metal cation, based on the weight of the substrate. 19. A process according to any of the preceding claims in which the thermotransfer printing step c) is conducted at normal pressure using a dispersion dye which is capable of forming a chelate compound with the metal used in step b). 20. A process according to claim 19 in which the dispersion dye is an azo or anthraquinone dye. 21. A process according to claim 20 in which the azo dye has the formula: in which A and B are the same or different and each is an aromatic or heteroaromatic ring system. 22. A process according to claim 21 in which ring systems completed by A and/or B are phenyl or naphthyl rings, each optionally substituted with C r C 4 alkyl, C r C 4 alkoxy, hydroxy, halogen or amino optionally substituted with - alkyl or C r C 4 hydroxyalkyl groups. 23. A process according to claim 20 in which the anthraquinone disperse dye has the formula: in which R is hydroxy or NHR , Rj is hydrogen, C C 4 alkyl which is optionally substituted by hydroxy or Rj is phenyl which is optionally substituted by C 1 -C 4 alkyl; and R 2 , R 3 , R 4 and R 5 are the same or different and each is hydrogen, hydroxy, C 1 -C 4 alkyl, C C 4 alkoxy, chlorine, bromine, cyano, nitro, CONH 2 , C r C 4 alkoxycarbonyl, phenoxy in which the phenyl moiety is optionally substituted by C r C 4 alkyl, or phenoxysulphonyl. 24. A process according to claim 23 in which the anthraquinone disperse dye has the formula: in which R j , R 2 , R 4 and R 5 are as defined in claim 23 and R 6 is hydrogen, hydroxy or amino. 25. A process according to claim 23 in which R 4 and R 5 are hydrogen and R 2 is hydrogen or phenoxy. 26. A process according to any of the preceding claims in which the substrate is glass fibres. 27. A light-, wet- and rub-fast substrate printed by a process claimed in any of the preceding claims.

Inventors: FREIERMUTH BEAT, HOEHENER ALFRED, FREIERMUTH, BEAT, HOEHENER, ALFRED
Applicants: CIBA GEIGY AG, FREIERMUTH BEAT, HOEHENER ALFRED, CIBA-GEIGY AG, FREIERMUTH, BEAT, HOEHENER, ALFRED
Application year: 1994
Main classification: C03C25
IPC codes: B41M1, C03C25, C23F1, D06P3, D06P5